HUE028428T2 - Separating sequence for hydrocarbons from mild thermal splitting - Google Patents

Description

The indention relaies ίο a process for sepomting hydrocarbons in a plait íbr producing hydrocarbons írom a liquid hydzoearbonaceoos input by means of cracking, » wherein the product ps from the cracking which comprises gaseous hydrocarbons and: is formed as cracked gas Is compressed apd dried, ® and: is conducted as a feedstock into a separation Mage (hereinafter: front end C3/C4 separation), * in which the cracked gas Is separated into a hydrocarbon fraction composed of bydroeafhons hasdng: not more than 3 carbon atoms and a hydrocarbon fraction composed of hydrocarbons having at least# carhop atoms, * wherein the front end C-3/C4 separation:, In: terms of process technology, bas a €14 absorber and a depropanizer, :* wherein a hydrocarbon If action composed of hydrocarbons having not more than 3 carbon atoms is obtained as a gaseous top product from the C4 absorber, * and wherein ß liquid hydrocarbon fraction composed of hydrocarbons having at least 4 carbon atoms is obtained as a bottom product of foe depmpanimo

In a plant for production of hydrocarbons, called an olefin plant, the hydrocarbons or oleins are produced by cracking of bydrocarbonaceous inputs. The hydro-carbonaceous Inputs are either in the liquid or gaseous phase, and are converted to sherfer-chain Irydmcarhons by means of thermal or catalytic cracking with or without steam. The mixture of predominantly damn-chain olefins formed in the cracking is referred to as cracked gas or crude gas. In the case of cracking of a liquid hydro-carbonaceous inpug the cracked gas is usually conducted as an input into an oil sertibbing. In the oil scrubbing, the cracked gas is eooied, and longer-chain hydrocarbons remaining,: for example cokepaitieles and heavy oil components, are scrubbed; not of the cracked gas,: Subsequently, the cracked gas le conducted imn a water scrubbing for further cleaning and cooing* and compressed in the cracked gas compressi on. In the cmeMng: of a gaseous hydrocarhonaceons input, it is usually possible to omit the oil scrubbing. Subsequently, the cracked gas, according to the prior art is freed of fetlhor impurities, such m carbon dioxide andihydrogen sulfide. In an alkali scrubbing and dried.

The cleaned and dried eraéhed gas now consists of a mixtee of the desired olein products and by “products. In order to he able to utibae the desired olein products, the mixture has to be separated into the iirdiyidml oleip: coustitueats.

According to the prior art, such a process tor sepambug; hydrocarbons begins either with a separation stage in which oleins having at most 2 carbon atoms arc separated from oleins having; at least 3 carbon atoms (iront end Cj/C i separation) or a separation stage in which oleins having at most 3 carbon atoms ate separated harm oleins having at least 4 carbon atoms; fiord; end (¾¾¾ separation^

If the separation sequence begins with separation, the olefin iaction formed with at most 2 carbon atoms (¾.. feeilonh aier a cafolytic hydrogenation for removal of acetylene, is passed to a where it is divided into its individual fractions. This separates the fonction foom the methane and hydrogen fraction. The remaining feaetlon of hydrocartsoss having at least 3 carbon atoms (Cm if action) is conducted into a separation stage (deprppanker) in which the bottom product obtained is a fraction of hydrocarbons having at least 4 carbon atoms (€# faction), in. the depropatttaer,: an olefin fraction of hydrocarbons having 3 oaf boa atoms '(€$ fraction) is obtained, via the top:. The (¾ fraction is Stfosequently likewise eatalyticaily hydmgcBdfed: prior to foe further processing thereof.

In the context of this application, a hydrocarbon fraction consisting of hydrocarbons having n: carbon atoms; is referred to as a C;; fraction, if fois hydrocarbon fraction Consists of hydrocarbons having at least n carbon atoms, the hydrocarbon fraction is referred. to as a C.T, fraction, A fraction composed of hydrocarbons having a maximum of n carbon atoms is referred fo as a €»,· fraction.: n here represents the natural numbers 1,2, 3.4,., Á separation stage in which hydrocarbons; having;2; or more carhop atoms is obtained as a liquid bottom product is referred to in the context of this; application as a demeihmtker, A separation stage with a Cf., feaeifon as the bottom, product is referred: fo as a déethunizen Correspondingly, a separation stage with: a (¾.¾. bottom fraction is referred to as a depropanizer.

In the ease of a separation seqeeoeo aeooning to the prior art which begins with a firent end C3/C4 separatio«, « (¾. Section and a €3+ fraction are obtained at the pressure o f the compressed cracked gas. M the fell cracked gas pressure which exists, a sharp separation into a Ç3. fraction and a €4+ fraction is Impossible according; to the priorart, since the bottom temperature would he so high that an increased exterd of polymer tonnádon and hence unwanted deposit formation would occur in the Äther separation .sequence according to tie prior art the €h_ fraction after a catalytic hydrogenation is conducted iù a C j/Cfr separation, lire €3. fraction is separated into a €3 fraction and a. €2. fraction. Up. C^. feet» Is passed to a C3/C4 separation, where it is separated Into a (¾ fraction and a €V fraction, and the £3 fraction formed then has to be catalyticahy hydrogenated, thus, according to the prior art, both in the ease of a separation sequence with a front end C2/C3 separation and In the ease of a separation sequence with a front end C3/C4 separation, 2 independent catalytic hydrogenation stages with the corresponding tubular reactor and fixed bed reactor are neederh

Ills 101006010519 proposes an alternatlye process tor separation of oleins, f)fr 102000010519 discloses a separetion sequence with a €4 absorber which yœ#s at full cracked gas pressure, and a depropanizer which is operated at a pressoze of 8-12 bar. lire combination of €4 absorber and depropanizer separates the olefins into a Cfo frae&n and a €4?. fraction. The (¾. fraction is then folly compressed wad; conducted to foe catalytic hydrogenation, while the Cfo. fraction is discharged for fcirer processing. After the catalytic lydrogenadon, the €3,fipetfon is sahpeted to a C3/C3 separation and separated into a €2·· fraction ami a €.? fraction. T he Cfr. fraction is passed, onward is input into the knv-temperature separation section, while the £3 fraction is condaeted to further processing, A similar: separation sequence for a liquid hydrocarhonaeeoits Input is described in DE 10200993:1455. In the separation sequence disclosed here, a €4 absorber is likewise combined with a depropanizer, the Ç* absorber being operated at foil cracked gas pressée and the deprppspfer at a pressure between a bar and 12 bar, Aber the catalytic: hydrogenation, faciioa is subjected to a Ç2/Ç» separation, the C3. fraction being: separated in a column into a €% ffetion mâ a C2/tb fraction. The fruther separation is effected i» a .second column with: two: sections separated in t ermn of process technology, tbc agpr section being designed as a denfemnizer and: tile lower section as a dCefernzer, In the demetlumizer, dissolved methane and dissolved hydropn are Gripped opt of die condensates fion-i fe lowdemperatuzc cooling, in the deethanizer, aC2. taction mâ & Cs 'tiefes m formed. I'he Q fraction £3 is obtained as the bottom product. A portion of the lipid C2 frontion from the demethanizer serves as a return stream. The bottoms:!» are feled elfer with cracked gas or with hot % coolant or with hot mixed coolant The C* fractions from the second column, wbieh are drawn off as gas and Icfuid product laterally from the bottom of the demethanizer of fe second Column, are supplied to a €2 splitter. Ethy lene is obtained therein as fe top product.

It is an object of the present invention to configure a process of the type specified at the outset such that the energy intensity and appratus complexity for seprafron of hydrocarbons Is minimized. More particularly, the energy miensity in the sepration of a cracked :gas formed in the cracking and having a rafe of ethylene to propylene of close in 1,: especially below 1, is to be minimized,

The stated object is achieved by the eombinetioh of feafees of independent daim I, Advantageous configurations of the Invention: are speif ed in the dependent claims:.:

According to the Inventions the separation sequence far fe: hydrocarbon products of the cracked gas: begins with a front end C3/C4 separation, which, comprises a further process stage of a C2/C4 separation stage. This further Ö/C4 separation stage is arranged between the €4 absorber and the depropanizer,

In the case of a relatively high proportion of louger-ehlu» hydrocarbons in the cracked: gas, he. spcifically in fe ease of a cracked gas with a high,€4+ content, both the amount of condensate and the proportion of dissolved components in fe condensates nise during fe compression of the cracked gas, such that a sharp front end C3Æ4 separotion becomes more dlffiefot^^ However, the present invention solves this problem completely. The additional C2/C4 separation stage reduces the cooling requirement particularly for the top product of the depropanizer, and thus minimizes the energy intensity of the separation sequence.

According to the invention, a further C2/C4 separation stage is arranged^ between the C4 absorber and the depropanizer. In this separation stage, a separation of C >. and Cfo components takes place* the (¾ eotnponents In. this separation stage being present both. In the gaseous tops and in the liquid bottom product, such that the top gas foam this separation stage cap be condensed at a higher temperature level. This prevents a temperature increase in a region of enhanced polymer formation in the bottom product. 1 he overall inventive front end C3/C4 separation consisting of the C4 absorber, the C2/C4 separation stage and the depropanizer allows, overall* à sharp separation, in terms of process technology, of the compressed cracked gas formed In the cracking imo a Cj, traction and a Cfo traction. The tempera tares are always kept within ranges at which no polymers Or deposits are formed. The Inventive eonfoinahon of the C4 absorber, the C2/C4 separation stage itttd the depropanizer, and nonsharp separation, allows the pressure of the efotdensateS obtained to fee reduced grad ually over the ^separation process such that a €** fraction not containing any hydrocarbons having fewer than four carbon atoms is ohfoined in the depropanizer without such a rise In die bottom fomperature as to cause polymer or deposit formation, and nhntrofoation of the energy intensity for the separation.

In a profored configuration of the invention, the 04 absorber and the Ç2/C4 soparaffon stage are operated at a pressure between 18 and 20 bar, the C2fC4 separation stage preferably befog operated at somewhat higher prossoro than the 04 absorber. This eonSgaraion of foe invention allows supply of the compressed crocked gas at foil cracked gas pressure directly to foe C4 absorber.

In a preferred ennhgnration of foe invention, the (14 absorber and foe C2/C4 serration stage are combined in one coteau. In fois eenlgmraiioo, C’4 absorber and C2/C4 separation stage are eoitefoed in one cohmm, but form separate séchons of this eolnnm is teas of process technology, Accordingly, the gmmm- Iwél of both sections of the process (€4 absorbs C2A34 separation stage) is Ms configmviiion of the invention is the same.

Is an alternative configuration of the Invention, 04 absorber and C2/C4 soparaiion stage are difeent colurnns. In this alternati ve eon%inatton of the invention, the €4 absorber and the Ç2/C4 separation stage which are dearly separated in terms of process technology are also divided in apparatus terms into two separate columns. In this conflgnration of the invention, a bottoms pump tor fc Ç4 absorber is mqnlred. The C2/C4 separation stage is operated at somewhat higher pressure than the 04 absorber.

Advantageonsly, the bottom product of the C2/C4 separation stage is supplied to the depropnizer. The (22iC4 separation stage separates the hydmearhoss Into a Cb„ traction and a (¾ traction. The Cj*. fraction is obtained as the bottom prod net. This bottom product Is advantageonsly supplied to the depropanizer, whom the (¾ framion is removed and a pons €4* fmetlon is obtained as the hotmm pmduet

The depropanizer is preferably operated at a. pressure between 10 and 12 bar.

More preferably; the cranked gas to be separated contains ethylene and propylene in a ratio of 1 or less than i. The conditions of the cracking have been set correspondingly. The ad vantages of the invention are manifested. particularly when the conditions of the cracking have been set such that the propylene content in the cracked gas corresponds to the ethylene content or is greater than die ethylene content- In the case of such a cracked gas, it is pardoulariv possible through, the Invention to conduct a front end Ch/Ch separation in asharp manner without polymer or deposit formation in the apparatus Involved.

Preferably, a ratio of ethylene to propylene of 1 or less than I is achieved by adding a certain proportion of saturated hydrocarbons f pretetably between 3% by weight and 4§% by weight, more preferably between 5% by weight and 30% by weight and especially between 15% by weight and 25% by weight! to the liquid bydrocarbonaceeus input consisting ρίβΐ to the thermal cracking. The rhetmal crocking takes place appropriately under mild conditions (preferably TdCFC-SCHT'C, and/or 2.5 bar abs ~ 4 bar abs). Advantageously, one or more recycled €4;. fraction(s) as saturated hydrocarbons are added to foe liquid input,

Ifoe present invention Is parikuladly sohable for separation of hydroembons in a plant for production of hydrocarbons front i liquid hydrocarbonaceous input by means of cracking.

More particularly, It is possible with the process according to the invention to minimize the energy intensity in a separation sequence for a cracked gas as formed particularly in the cracking of liquid hydtocarbonaceous inputs. Especially in the case of a cracked gas having a relatively high Co- content, it is possible in the case of the Inventive from end C3/124 separation to achieve a sharpseparation into a C3. fraction and a €4+ fraction of the cracked gas without Increased polymer or deposit formation In the apparatus involved.

The invention is to be illustrated in detail hereinafter with reference to the two working examples shown in figures I and 2.

The %urea;fo,ow;

Figure I a configuration of the invention ín which (he €4 absorber and CÄ4 separation stage arc different columns,

Figure 2 an alternative eooigoraiion of the invention In which €4 absorber and: C2A14 separation slap arc arranged in one column.

Figure I. shows one configuration of the process according to the invention for separation of hydrocarbons in a plant in which a liquid hydroearbonaceous input is cracked such that the cracked gas formed in the maciing has an ethylene to propylene content o f hot shore than ! of less. The cracked gas ! formed as the cracking product is conducted as an input into m oil scrubbing (not shovn§. In tbs oil scrubbing, foe ceaeked gas is cooled aad relatively long-chain hydepegrhons remnirang, lor example coke particles and heavy oil components, are separated out of the cracked gas. Subsequently, the cracked gas I is condiicted Into a «ter scrtfoblag (not shrrwn) for ferfocr cleaning and cooling and conducted if ont these into a thraevnage cracked gas cofopession 2a. in foe foree^iage cracked gas compression 2a, foe cracked gas is compressed to a pressure of approx, 2(1 bar, preferably 19 bar, arrd freed of apd gas eompratents, such as carbon dioxide and hydrogen sulfide, In a scrubbing 3, Subsequently, the cleaned, cracked; gas is precooled Is a precooler 4 and dried by rheans of the two dryers 5a and $b. Subsequently, foe actual separation sequence of Cracked gas ! begins.

The cracked gas cornpesslbn 2a beats tip foe cracked gas, and so cooling is necessary prior to the add gas scrubbing 3 (not shown), The condensate formed is conducted directly fora the depropanizer 8 (not shown), The acid gas components inevitably supplied to Éghg&yefoe-^kpitopmîmr 8-gas fisse I d via foe top and are recycled 12 to the cracked gas compression 2a. The condensates detailed In this section can be drawn off from any stage oft.be cracked gas compression 2a, but praimfoly, as In thi s working example, alter the 3rd stage of foe cracked gas compression: 2a,

The condensa te formed in the precooler 4 is supplied via foe dryer 3a to the C2/C4 separation stage ?- The top gas formed in the precooler 4 Is supplied via. the dryer 5b directly to the C4 absorber 6. Both €4 absorber 6 and the C2IC4 separation stage ? work at the foil cracked gas pressure between It and 20 bar, preferably 19 bar. The pressure in the C4 absorber 6 is slightly lower than foe pressure In the Ü2/C4 separation stage ?< The gaseous product formed in the 04 absorber# Is a pure C3„ fraction 15. This is compressed further In a fourth compression stage 2b and conducted to furfoer division 13, in which the ethylene and propylene products of value are then seprafod ont of this €3, fraction 15,

The bottom product 13 of the €4 absorber 6 is supplied to the C2/C4 separation stage 7, just lka the condensate from the dryer 5a. In the C2/C4 separation stage 7, the hydrocarbons having three cavort atoms are divided between tie gntoous top product and the liquid bottom product. The top product contains only a small amount of hydrocarbons having more than three atoms, and the Attorn product is free of hydrocarbons having fewer than two carbon atoms. Thus, in tie C2/C4 separation stage 7, a gaseous top product is obtained,: which constitutes ä €4. fraction M, The liquid bottom product ft of fc U2/C4 separation stage 7 Is a €h* traction If.In order to ensure that the top product 14 ofthe C2/C4 separation stage 7 contains only a low level of hydrocarbons having four or more carbon atoms, the C2/C4 separation stage 7 has a top condenser-7a.

The hottotp product; 18 of the U2C4 separation stage 7 is supplied to the deprppapiner 8 tor removal of the €4+ if action. The depropanizer 8 works at a pressure between 8 and 12 bar. The bo ttotn product 18 of the C2/C4 separation stage 7 is therefore decompressed Into the depropaniser 8. In thé depropaniser 8, a pure €4+ fraction forms •as. the hottom product 17, and is drawn off íhéreírom. The bottom product 17 of fhe depropanfoer Is tree of any (¾.. components. The top: product: 1,6 obtained trout the depropanigur Is a fraction which consists principally of hydrocarbons having three Pathos atoms. Using a heat exchanger 11, the top pmdeei Î6 of the dcptopnlser 8 is cooled further nod conducted into a separator 9. The gas phase 12 obtained in the separator Is recycled Into the cracked gas I prior to the three-stage compression 2a.

The Igfod f toduct of the separator 9 is supplied via a pump 19 as a return stream to the dgpropanfoet" 8,

The gaseous top product IS of the €4 absorber 6 is likewise cooled by means of a heat, exchanger :! I ami conducted into a separator 9.7'be lipid phase formed is supplied via the pump 10 to the C4 absorber 6, again as a return stream. The gaseous phase is compressed in the fourth stage of the cracked gas compression 2h and Cohiitotod m €3. fraction to the ethylene and propylene recovery 13,

Figure 2 works in a sittoiär manner to fc working example according to figure 1. Identical parts were labeled with the same reference numerals as in ligure I, In contrast to the working example according to ®gure 1, however, €4 absorber 6 and C2/C4 separation stop 7 are arranged here In one column.

Claims (5)

!. For the separation of strawberry hydrocarbons suitable for the production of spheroidal genes from hydrocarbon-derived starting material by cleavage, where the gas is formed by the gas-forming carbon dioxide (2a) and precipitates (b), which are the raw gas (I) of the abdominal cassette. as a material in a separating stage (hereafter referred to as C3 / C4 <d pre-selection), • raw gas fi) is selected from a hydrocarbon hydrocarbon consisting of 3 carbohydrates with a higher carbon content (Ia) and a hydrocarbon feakel (17) consisting of hydrocarbons having at least 4 carbon atoms. «Aào! the C3 / C14 separation front is technically a € 4 abscess main) and a depropsor (8; - where the € 4-fold (b) is a gas-shaped headlamp) is a hydrocarbon phosphorofoil of one of the most potent hydrocarbons (3); Auxiliary Fluidizer (8) is provided with a liquid carbohydrate liquid, at least 4 divergent x-ray rods (17), as described above, wherein the separation portion comprises an additional cost-per-thetry (?), wherein the separation level of € 2rC4 is (7). ) arranged between the G4 abortifier (6) and the depropanthorse (8). %,: A series of cylinders of claim 1, characterized in that the C4 separator (6) and the C2 / G4 separation column (7) are present. At a pressure of between 8 bar and 20 bar, the Δ2 / C4 separation step (7) is preferably operated at a slightly higher pressure than that of (24-absorber (6), 1). characterized in that the € 4 ~ absorber | b) and the G2 / C4 separation stage??} are combined in one column, 4. The burst according to claim 1 or 2, characterized in that the separator C4 (6) and the separation stage C2 / G4 (7) are separate columns. Method according to any one of claims 1 to 4, characterized in that the spine (18) of the edge selection stage (7) is fed into the depropanizer (8), 6. A burst according to any of the claims, characterized in that the depropanizer unit has an operating pressure of about 1.2 bar, 7. Process according to any one of claims 1 to 3, characterized in that the deproganate (I) fossil product is obtained with at least 4 carbon atoms. I> 1-7 A press according to any one of claims 1 to 4, characterized in that the raw gas (!) contains ethylene and propylene in a ratio of 1 or less than 1, where the cleavage conditions are adjusted appropriately.